A better understanding of geneticdiversityincotton cultivars is needed to make the most of the genetic resources and guarantee continuing improvements in the breeding programs. Our objective was to evaluate the geneticdiversity among cottongenotypes from the top breeding programs in Brazil and recommend hybrid combinations that would increase variability. The field experiments we conducted on three cottongenotypes from each of the following Brazilian breeding programs: EMBRAPA, MONSANTO DELTAPINE, FIBERMAX, IMA, TMG and UFU. Several phenotypic evaluations were carried out at V5, B1, full flower and full maturity. Moderate genetic divergence was observed among the genotypes from these breeding programs. Hybridization of the BRS 433 FL B2RF and FM 980 GLT genotypes would likely produce segregating populations with greater geneticvariability, yield potential, lint yield and desirable fiber quality. Maturity, micronaire and fiber length were the strongest contributors togenetic divergence.
ABSTRACT: The characterization and study of geneticdiversity between accessions of the germplasm bank contribute to increased efficiency in selecting parents to be used in a breeding program. Thus, the objective of this work was to evalute genetic divergence by means of multivariate procedures among 71 genotypes of Coffea canephora var. kouilouensis and 56 genotypes of Coffea canephora var. robusta of the Germplasm Bank of the breeding program of Empresa de Pesquisa Agropecuária de Minas Gerais (EPAMIG) in a partnership with Universidade Federal de Viçosa. Together with this work, it was also aimed to indicating higher and more divergent genotypesto be used in intrapopulation crossings aiming at exploring greater geneticvariability within segregating families. In July 2009, two experiments involving the genotypes of C. canephora var. kouilouensis and two experiments involving the genotypes of C. canephora var. robusta were deployed at the Experimental Farm EPAMIG in Oratorios, Minas Gerais, in an experimental randomized complete block design with five replicates and experimental plots consisting of a plant. The study was based on an evaluation of six morpho-agronomic traits in July 2010 and 2011. The indication of superior genotypes was determined using the selection index based on the sum of rank. Intrapopulation crossings between higher and divergent genotypes were indicated for creating greater geneticvariabilityto be used in the offspring aiming at increasing the probability of obtaining higher individuals.
The SOM method has been shown to be an efficient way of identifying patterns of similarity, as shown by Mwasiagi (2011), who used the SOM technique to distinguish cottongenotypes. This author concluded that the method was efficient for separating thin wires from coarser ones, and the samples that were dispersed on the map would be outliers, implying irregularity of the material. Smith et al. (2003), studying the SOM efficiency for organizing web pages through navigation patterns, obtained a satisfactory result and concluded that the method can be easily incorporated; however, this needs to be developed for large scale applications. A similar conclusion was found by Fritzke (1994), who studied the map efficiency for supervised and unsupervised learning.
third, fiber percentage, average production per plant, yield and cotton fiber quality. The results were subjected to individual and joint analysis of variance and the genetic divergence was estimated according to multivariate procedures (Mahalanobis' generalized distance and Tocher's optimization method). The dissimilarity matrices were summed to estimate the genetic divergence, considering both growing periods. Geneticvariability was found among the genotypes evaluated, in both the main season and off season. The characteristic that most contributed to the genetic divergence in the main season was the production per plant and, in the off season,
The genetic divergence of melon genotypes belonging to momordica group, collected in five Brazilian States, was estimated, and the relative contribution of the morphological characters was determined for the geneticvariability. The experimental design was randomized blocks, with four replicates. We evaluated 19 accessions of melon, momordica group, two accessions of cantaloupensis group and two commercial cultivars of inodorus group. These genotypes were characterized by 42 morphological descriptors. The data were submitted to Tocher and UPGMA grouping methods using the genetic dissimilarity matrix, using Mahalanobis’ distance. Singh criterion was used to identify the relative contribution of each character to the genetic divergence. Four groups of similarity were obtained in both multivariate techniques, with agreement between hierarchical UPGMA and Tocher grouping methods. The characters: pistil scar size, soluble solid content, seed length, fruit length and cotyledon length contributed with approximately 53.86% togenetic divergence among genotypes.
ABSTRACT - The continuous development and evaluation of new genotypes through crop breeding is essential in order to obtain new cultivars. The objective of this work was to evaluate the genetic divergences between cultivars of upland cotton (Gossypium hirsutum L.) using the agronomic and technological characteristics of the fibre, in order to select superior parent plants. The experiment was set up during 2010 at the Federal University of Ceará in Fortaleza, Ceará, Brazil. Eleven cultivars of upland cotton were used in an experimental design of randomised blocks with three replications. In order to evaluate the geneticdiversity among cultivars, the generalised Mahalanobis distance matrix was calculated, with cluster analysis then being applied, employing various methods: single linkage, Ward, complete linkage, median, average linkage within a cluster and average linkage between clusters. Geneticvariability exists among the evaluated genotypes. The most consistant clustering method was that employing average linkage between clusters. Among the characteristics assessed, mean boll weight presented the highest contribution togeneticdiversity, followed by elongation at rupture. Employing the method of mean linkage between clusters, the cultivars with greater genetic divergence were BRS Acacia and LD Frego; those of greater similarity were BRS Itaúba and BRS Araripe.
Crop maturity duration is critical in all agricultural crops. However, in the cotton crop, it is of prime importance because short duration cotton varieties ensure food security by allowing in time sowing of wheat. Incotton, a number of plant characters are involved indetermining the maturity duration of the crop thus making it very complex. Considering the vitality of this issue, different morphological and phenological traits related to earliness incotton were studied using diallel analysis. It is a useful biometric technique which gives comprehensive information on the genetic components of variation. In previous investigations node for 1st fruiting branch and days to 1st boll opening were used as effective selection criteria for the estimation of earliness incotton [6, 12, 26]. In the research work presented here, although additive component was significant in the inheritance of days taken to appear first square yet the low heritability of this trait made it unfit to be used as earliness indicator. Besides low heritability, square abscission is common due to environmental stress in terms of high temperature and insect damage as reported by  among other phenological measures, days to first flower and days to first boll opening, vertical and horizontal flowering intervals were controlled by additive variation. Heritability estimates recorded for these traits were reliable due to which these could be used as efficient indicators of earliness in breeding programs conducted toimprove maturity duration incotton crop [5, 13, 17, 25]. In other studies [11, 22, 26] reported that days to 1st flower, days to 1st boll opening, and node for 1st fruiting branches were additively controlled and in contrast the studies by  showed that days to flowering and days to boll opening were controlled by non-additive gene effects. Parents used in this experiment showed reduced flowering duration which could be of great utility in avoiding boll damage caused by the late season insect attack. Another phenological character studied was boll maturity period for which parents showed delayed ripening. This might be accounted for a significant environmental component of variation because earlier researchers have indicated that boll maturation period is largely temperature dependent
While overall the Pimenta longa germplasm revealed a high degree of polymorphism, the collected P. aduncum germplasm contained a low geneticvariability. The group formed by the P. aduncum individuals was very homoge- neous with a degree of similarity close to 1.00, indicating that there is essentially no geneticdiversity for this species in the germplasm collection. This high degree of mono- morphism suggests the possibility of high rates of self- pollination. This is supported by a study of the pollination ecology of Southeastern Brazilian Piperaceae, in which P. aduncum had elevated levels of spontaneous self- pollinization (Figueiredo, 1997). There are little genetic differences among individuals from the same population in self pollinating species and most of the geneticvariability is found among populations (Jain, 1976; Loveless and Hamrick, 1984; Linhart and Grant, 1996). Also, P. aduncum has a tendency to form large stands of plants that reproduce vegetatively. All the genotypes analyzed in this group are from the Juruá valley (Figure 1), and may there- fore be part of a same large, relatively homogenous popula-
was eliminated from the diversity analysis, the estimate of the cophenetic correlation coefficient was 0.018, indicating the importance of this variable in the discrimination of genotypes. The most important of the 22 descriptors were therefore ranked: presence of anthocyanin in the stem, grain color, secondary pod color, pod profile, yield, position of the pod apex, pod profile, seed flattening, and plant architecture. On the other hand, the nine least important and dispensable traits were ranked as follows: seed gloss, seed uniformity, presence of anthocyanin in the cotyledons, primary color of dry pod, growth habit, 100-grain weight, shape of pod apex, days from planting to flowering and presence of anthocyanin in the hypocotyl. Although the trait 100-grain weight is considered very important in the reduction of grain size (Singh et al. 1991), it was ranked among the descriptors of lower contribution for the study of geneticdiversity among genotypes. The reason was probably because 96 % of the genotypes belong to the Mesoamerican gene pool (small and Median grain). The least important descriptors detected here were the same as reported in previous studies (Rodrigues et al. 2002, Chiorato et al. 2005), except for growth habit.
The objective of this study was to compare methods of multivariate analysis on the evaluation of geneticdiversity of mini tomato and to identify promising genotypes with resistance to pests. The experiment was conducted at the Vegetable Experiment Station of the Universidade Federal de Uberlândia, Monte Carmelo campus, from April 2013 to November 2016. The experimental design was a randomized complete block design with 16 treatments and four replications totaling 64 plots, and each plot represented by five plants. Sixteen genotypes were characterized, 12 from the F 2 RC 1 generation, obtained through the interspecific crossing between the wild access LA-716 (Solanum pennellii) and pre-commercial lines of mini tomato (UFU-73 and UFU-2) (Solanum lycopersicum) and the UFU-2 lines. The content of acyl sugar, the amount of glandular trichomes (types I, IV, VI and VII), twospotted spider mite and whitefly resistance were evaluated. We concluded that there exist geneticvariability between the genotypes. The number of groups formed by the canonical variated analysis was higher (four groups) than that obtained by the Tocher method (three groups) and UPGMA (three groups), demonstrating a greater discrimination power. The Tocher and UPGMA methods were consistent in the analysis of the genetic divergence in pest resistant germplasm of tomato, with the acyl sugar content being the most important variable. Genotype UFU-73-F 2 RC 1 # 11 is resistant to pest attack, while the other studied lines have intermediate resistance.
Along the last decades, some areas within biomes like the Atlantic Forest and Cerrado, have been intensely exploited for cultivation, disintegrating the native vegetation of biomes in small and isolated frag- ments (Myers et al., 2000; Klink & Machado, 2005). Consequently, the conservation of endemic plants un- der high anthropic pressure, mainly those plants from the Cerrado, represents a great world challenge (Felfili et al., 2004; Giulietti et al., 2005; Brandon et al., 2005). The molecular markers technology is an impor- tant tool for biodiversity conservation programs of plants under risk of extinction, since it allows the estimation of the geneticvariability among and within populations and, consequently, provides information on the genetic structure of those natural populations. The Random Amplification of Polymorphic DNA (RAPD) (Williams et al., 1990; Welsh & McClelland, 1990) facilitates the identification and the differentiation of genotypes, for a first screening of geneticvariability, and allows corre- lating it to phenotypic expressions and determining pos- sible phylogenetic relationships among different species germplasms or populations (Ferreira & Grattapaglia, 1998; Daher et al., 2002; Kroth et al., 2005; Sandhu et al., 2006). Through the RAPD technique it is possible to identify atypical genotypes that can be introduced into germplasm banks, permitting its multiplication in large scale when required (Lacerda et al., 2002).
These estimates are indicators of the genetic nature and probability to obtain superior genotypes when it comes to the root growth in triticale. Few genes, low environment influence and high proportion of the additive variance in expressing the genetic variance imply more facility toimproveto obtain genotypes with tolerance to aluminum toxicity, besides allowing early selection in the first segregating generations.
Cajanus cajan (L.) Millsp. (pigeon pea) is one of the im- portant leguminous crops. It is cultivated predominantly in tropical and subtropical regions. Because of the vast natural geneticvariabilityin local germplasm and the presence of numerous wild relatives, India is considered the primary center of origin (Van der Maesen 1980) and one of the largest pigeon pea producers. It occupies an area of about 3.4 million ha with an average annual production of 2.89 million tons from the global annual production of 3.49 mil- lion tons (DAC 2011). Despite the large area under pigeon pea cultivation in India, the average productivity (741 kg/ ha) is remarkably low mainly because of yield losses caused by several biotic and abiotic stresses. Fusarium wilt (FW) and sterility mosaic disease (SMD) are the main biotic dis- eases of economic concern. Recent advances in pigeon pea genomics, including whole genome sequence information (Singh et al. 2012; Varshney et al. 2012), have resulted in a tremendous increase in the amount of genomic resources.
ABSTRACT - Characterizing geneticdiversity based on evaluations involving germination and seed vigor, is a fundamental stage in starting the development of a cultivation system for Calotropis procera. Thus, this study aimed to estimate geneticdiversity among 35 C. procera genotypes based on germination and vigor of seeds stored for 1 year. The genotypes, which originated from areas in Paraíba (Brazil), where they occur naturally, were collected and stored in March 2014. In order to evaluate the physiological potential of the seeds, two experiments were conducted between March and April 2015. The first involved a propagation test conducted in a germination chamber, while the second involved an emergence test in washed sand, performed in polyethylene trays in a screened environment under uncontrolled conditions. In both experiments, an entirely randomized design was used, with four repetitions of 25 seeds per genotype. The characteristics evaluated were germination, average daily germination, daily germination speed, the speed of germination index, the plantlet vigor index, emergence, the speed of emergence index, total length, and total dry mass. The results showed that geneticvariability exists among the C. procera genotypes for variables involving germination and vigor of seeds stored for 1 year. Also, emergence, total dry plantlet mass, and germination characteristics contribute most to the genetic divergence among C. procera genotypes.
Analyses of restriction site differences in the ITS region were not sufficiently sensitive to detect differences among the populations and pathotypes of S. solani attacking two different crops. Given the taxonomic controversy due to the conidial differences between isolates pathogenic on cotton and tomato, restriction site homogeneity provides support for both as members of the same species. However, given the lack of variability observed in Alternaria, complete clarification will only be achieved following sequencing of ITS region. Similar results were obtained with Fusarium solani (Mart.) Appel & Wollenw. Emend. Snyd. & Hans., causing sudden death syndrome of soybean [Glycine max (L.) Merrill] (Achenback et al., 1997) and Mycosphaerella pinodes Berk. & Blox. and Phoma medicaginis Pass., causing Ascochyta blight of pea (Pisum sativus L.) (Onfroy et al., 1999).
Using 12 RAPD primers, the 21 lines could be classified into 3 groups, variation were detect in 17 lines of group II, duplicate lines were identified in groups I and II. This type of information is essential for germplasm conservation and improvement. Knowledge of the pedi- gree of a cultivar may be useful for the identification of sources of genes of interest and understand its role in ge- netic variability. However, the pedigree information is not always available for the breeder. In these cases, molecu- lar markers can be used as an accurate tool to detect simi- larity/divergence and identificate duplicated bean lines or accessions among bean cultivars. Molecular analyses, in conjunction with morphological and agronomic evalua- tions of cultivars are recommended, because they provide complementary information and increase the resolving power of geneticdiversity analysis (Singh, et al., 1991c).
Because of the potential of the pigeonpea as a forage legume, the Brazilian Agricultural Research Corporation (Embrapa Cattle-Southeast, state of São Paulo-SP) has germplasm collections of selected genotypes with desirable agronomic traits such as high yield, quality of forage and lowest tannin content (Godoy et al., 1995). Over time, the selected genotypes showed phenotypic segregation in subse- quent generations. Therefore, these genotypes were self-fer- tilized and subsequently selected in order to obtain inbred lines (Godoy et al., 1994, 1997). Several studies have been conducted to characterize genotypes and inbred lines of the pigeonpea and provide basic information for breeding. The geneticvariability of a partial set of accessions from this col- lection was assessed using Random Amplification of Poly- morphic DNA (RAPD) molecular markers. Results showed low geneticvariability and the need to broaden the genetic
The Mahalanobis distances from the variation in the components of the grains ranged from 0.11 to 251.02 and indicated geneticvariability among the accessions. The most divergent pair of accessions was PI417360/CD01RR8384, followed by PI417360/B3PTA213-3-4 and PI417360/ BARC-8. The most similar pair of accessions was CS3032PTA276-1-2/CS3032PTA190-5-1, followed by UFV18/M-SOY8914 and BRSMG Garantia/ CD983321RR. Regarding the importance of the variables togeneticdiversity, the contribution of each variable togeneticdiversity was equal to 33.28, 20.81, 20.85, 13.54, and 11.52% for the protein, oil and fatty acids oleic, linoleic and linolenic contents, respectively, revealing that protein content is the most informative character and acid linolenic content the
Thus, cotton breeding programs aim to develop genotypes that simultaneously meet a series of attributes of economic interest. However, selection based on one or a few traits may result in unfavorable changes in others, due to the presence of negative genetic correlations between them. Shen et al. (2006) reported negative correlations among agronomical and quality traits, such as fiber length with lint percent and lint yield, and among seed cotton yield with fiber strength and fiber length. Lin et al. (2005), when working with linkage mapping of cotton for assessing cotton fiber quality, found that fiber length was negatively correlated with micronaire values. Negative correlation among fiber strength and short fiber content were also reported by Ulloa (2006). This suggests that it is not satisfactory toimprove one variable through indirect selection in another.
The impact of NoV infections in outbreaks and spo- radic cases of acute gastroenteritis has been character- ized by the emergence of novel strains, which have been identified using new protocols that allow for the rapid diagnosis and molecular characterization of those vi- ruses. Protocols using primers that amplify regions A and B have been widely used for viral detection because this is a highly conserved region (Ando et al. 1995, Ji- ang et al. 1999, Fankhauser et al. 2002). Still, regions C and D, which comprise different partial sequences of the gene encoding for VP1 protein, are recommended for the characterization of different genotypes (Mattison et al. 2009). Region D, used in this study, was previously de- scribed to efficiently genotype NoV for characterization and has been used as an alternative to full sequencing of VP1 that relies on about 1,600 nucleotides (Vinjé et al. 2004). The high geneticvariability of region D may explain why we failed to amplify all previously detected strains by the polymerase conserved region. Recently, Mattison et al. (2009) suggested the use of region C for genotype characterization and region D for character- izing variants of GII.4 samples. Certainly, new protocols for NoV characterization will emerge in order to increase the number of genotyped samples that encompass more variants of NoV. Further studies using different set of primers or complete VP1 sequencing must be performed in order to achieve this goal.